Investigation of mechanisms by which immunoregulatory signals are transmitted to T-lymphocytes to cause activation or suppression of their activity. Project attempts to examine both antigen and allogeneic receptors on T-lymphocytes and the means by which they may be activated, blocked or stimulated to active suppression of T-cell functions. In particular, the role of immune complexes and the related role of anti-idiotype antibodies in the regulatory process will be examined. The interaction between antigen, antibody, complement, anti-idiotype immunoconglutinin and rheumatoid factor will be examined in the make-up of immune complexes to determine the role of each, individually or acting in concert, to produce effects on T-cell activation or effector function. In addition, attempts will be made to identify immune complexes in disease states such as juvenile diabetes and hepatitis to determine what role they may play in vivo in the suppression of cell-mediated immunity in these diseases which are related to latent or persistent viral infections.